AAPM Task Group 119 has produced quantitative confidence limits as baseline expectation values for IMRT commissioning. A set of test cases was developed to assess the overall accuracy of planning and delivery of IMRT treatments. Each test uses contours of targets and avoidance structures drawn within rectangular phantoms. These tests were planned, delivered, measured, and analyzed by nine facilities using a variety of IMRT planning and delivery systems. Each facility had passed the Radiological Physics Center credentialing tests for IMRT. The agreement between the planned and measured doses was determined using ion chamber dosimetry in high and low dose regions, film dosimetry on coronal planes in the phantom with all fields delivered, and planar dosimetry for each field measured perpendicular to the central axis. The planar dose distributions were assessed using gamma criteria of 3%/3 mm. The mean values and standard deviations were used to develop confidence limits for the test results using the concept confidence limit = /mean/ + 1.96sigma. Other facilities can use the test protocol and results as a basis for comparison to this group. Locally derived confidence limits that substantially exceed these baseline values may indicate the need for improved IMRT commissioning.

Intensity-modulated radiation therapy (IMRT) represents one of the most significant technical advances in radiation therapy since the advent of the medical linear accelerator. It allows the clinical implementation of highly conformal nonconvex dose distributions. This complex but promising treatment modality is rapidly proliferating in both academic and community practice settings. However, these advances do not come without a risk. IMRT is not just an add-on to the current radiation therapy process; it represents a new paradigm that requires the knowledge of multimodality imaging, setup uncertainties and internal organ motion, tumor control probabilities, normal tissue complication probabilities, three-dimensional (3-D) dose calculation and optimization, and dynamic beam delivery of nonuniform beam intensities. Therefore, the purpose of this report is to guide and assist the clinical medical physicist in developing and implementing a viable and safe IMRT program. The scope of the IMRT program is quite broad, encompassing multileaf-collimator-based IMRT delivery systems, goal-based inverse treatment planning, and clinical implementation of IMRT with patient-specific quality assurance. This report, while not prescribing specific procedures, provides the framework and guidance to allow clinical radiation oncology physicists to make judicious decisions in implementing a safe and efficient IMRT program in their clinics.

Purpose To evaluate the accuracy and consistency of a gradient-based PET segmentation method, GRADIENT, as compared to manual (MANUAL) and constant threshold (THRESHOLD) methods. Methods and Materials Contouring accuracy was evaluated with sphere phantoms and clinically realistic Monte Carlo PET phantoms of the thorax. The sphere phantoms were 10–37 mm in diameter and were acquired at 5 institutions emulating clinical conditions. One institution also acquired a sphere phantom with multiple source-to-background ratios (SBR) of 2:1, 5:1, 10:1, 20:1, and 70:1. One observer segmented (contoured) each sphere with GRADIENT and THRESHOLD from 25–50% at 5% increments. Subsequently, seven physicians segmented lessions (7–264ml) from 25 digital thorax phantoms using GRADIENT, THRESHOLD, and MANUAL. Results For spheres < 20 mm in diameter, GRADIENT was the most accurate with a mean absolute %error in diameter of 8.15% (10.2%SD) compared to 49.2% (51.1%SD) for 45% THRESHOLD (p < 0.005). For larger spheres the methods were statistically equivalent. For varying SBR, GRADIENT was the most accurate for spheres > 20 mm, (p < 0.065) and < 20 mm (p < 0.015). For digital thorax phantoms, GRADIENT was the most accurate, (p-value < 0.01), with a mean absolute %error in volume of 10.99% (11.9%SD) followed by 25% THRESHOLD at 17.5% (29.4%SD), and MANUAL, at 19.5% (17.2%SD). GRADIENT had the least systematic bias, 4 with a mean %error in volume of −0.05% (16.2%SD) compared with 25% THRESHOLD at - 2.1% (34.2%SD) and MANUAL at −16.3% (20.2%SD) (p-value < 0.01). Inter-observer variability was reduced using GRADIENT compared to both 25% THRESHOLD and MANUAL (p-value < 0.01, Levene's Test). Conclusion GRADIENT was the most accurate and consistent technique for target volume contouring. GRADIENT was also the most robust for varying imaging conditions. GRADIENT has the potential to play an important role for tumor delineation in radiation therapy planning and response assessment.

This report describes the current state of flattening filter‐free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high‐dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out‐of‐field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity‐modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical applications are provided. Several of the areas in which future research and development are needed are also indicated.PACS number: 87.53.‐j, 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.bc

The efficacy of stereotactic body radiotherapy (SBRT) has been well demonstrated. However, it presents unique challenges for accurate planning and delivery especially in the lungs and upper abdomen where respiratory motion can be significantly confounding accurate targeting and avoidance of normal tissues. In this paper we review the current literature on SBRT for lung and upper abdominal tumors with particular emphasis on addressing respiratory motion and its affects. We provide recommendations on strategies to manage motion for different, patient specific situations. Some of the recommendations will potentially be adopted to guide clinical trial protocols.

Purpose-Using a retrospective analysis of treatment plans submitted from multiple institutions accruing patients to the RTOG #0236 non-small cell SBRT protocol, this study determines the dose prescription and critical structure constraints for future SBRT lung protocols that mandate density corrected dose calculations.Method and Materials-A subset of twenty patients from four institutions participating in the 0236 protocol and using superposition/convolution algorithms are compared. The 0236 protocol required a prescription dose of 60 Gy delivered in three fractions to cover 95% of the PTV volume. Additional requirements were specified for target dose heterogeneity and dose to normal tissue/ structures. The protocol required each site to plan the patient's treatment using unit density, and another plan with the same monitor units and applying density corrections was also submitted. These plans have been compared to determine dose differences. A two-sided paired student's t-tests were used to evaluate these differences.Results-With heterogeneity corrections applied, the volume of PTV receiving 60 Gy or more (V60) decreased on average 10.1% (SE=2.7%) from 95% (p=0.001). Maximum dose to any point 2 cm or greater away from the PTV increased from 35.2 Gy (SE =1.7 Gy) to 38.5 (SE=2.2 Gy).Conclusions-Statistically significant dose differences were found with heterogeneity corrections. The information provided in this study is currently being used for designing future heterogeneity corrected RTOG SBRT lung protocols to match the true dose delivered for 0236. KeywordsRTOG; Stereotactic Body; Radiation Therapy; Non-Small Cell Lung Cancer * Corresponding Author: 111 South 11 th St., Philadelphia, PA 19107, Tel:(215) 9551632, Fax:(215)9550412, ying.xiao@jefferson.edu.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. In addition, phantom measurements and calculations reported in the literature showed that reasonable accuracy and more importantly consistency from center to center could be achieved by simply not using the vendor's heterogeneity correction algorithm 24 . It was therefore decided not to allow tissue heterogeneity correction for calculating monitor unit settings for RTOG 0236 25 . As required by the protocol, all dose planning and calculation of monitor units for actual treatment were performed with all tissues assuming unit (water) density. However, in an effort to ultimately better understand these effects for improving future protocols, each plan was also calculated with software vendor supplied heterogeneity corrections and submitted for QA purposes. The computat...

In the largest early-stage NSCLC SBRT data set to date, a high rate of local control was achieved, which was correlated with a PD(BED10) of 105 Gy or more. Failures were primarily distant, severe toxicities were rare, and overall survival was encouraging in operable patients.

A substantial barrier to the single- and multi-institutional aggregation of data to supporting clinical trials, practice quality improvement efforts, and development of big data analytics resource systems is the lack of standardized nomenclatures for expressing dosimetric data. To address this issue, the American Association of Physicists in Medicine (AAPM) Task Group 263 was charged with providing nomenclature guidelines and values in radiation oncology for use in clinical trials, data-pooling initiatives, population-based studies, and routine clinical care by standardizing: (1) structure names across image processing and treatment planning system platforms; (2) nomenclature for dosimetric data (eg, dose-volume histogram [DVH]-based metrics); (3) templates for clinical trial groups and users of an initial subset of software platforms to facilitate adoption of the standards; (4) formalism for nomenclature schema, which can accommodate the addition of other structures defined in the future. A multisociety, multidisciplinary, multinational group of 57 members representing stake holders ranging from large academic centers to community clinics and vendors was assembled, including physicists, physicians, dosimetrists, and vendors. The stakeholder groups represented in the membership included the AAPM, American Society for Radiation Oncology (ASTRO), NRG Oncology, European Society for Radiation Oncology (ESTRO), Radiation Therapy Oncology Group (RTOG), Children's Oncology Group (COG), Integrating Healthcare Enterprise in Radiation Oncology (IHE-RO), and Digital Imaging and Communications in Medicine working group (DICOM WG); A nomenclature system for target and organ at risk volumes and DVH nomenclature was developed and piloted to demonstrate viability across a range of clinics and within the framework of clinical trials. The final report was approved by AAPM in October 2017. The approval process included review by 8 AAPM committees, with additional review by ASTRO, European Society for Radiation Oncology (ESTRO), and American Association of Medical Dosimetrists (AAMD). This Executive Summary of the report highlights the key recommendations for clinical practice, research, and trials.